WITH DATA AS (
    SELECT
        MONTHLY,
        IFNULL(NEW_MRR + EXPANSION_MRR - DOWNGRADE_MRR - CHURN_MRR, 0) AS MRR
    FROM
        MRR_DATA
    UNION ALL
    SELECT
        DATE(MAX(MONTHLY), 'localtime', '+1 month'),
        0
    FROM
        MRR_DATA
)
SELECT
    MIN(MONTHLY) AS YM,
    0 AS MRR
FROM
    DATA
UNION ALL
SELECT
    DATA.MONTHLY,
    SUM(PAST.MRR)
FROM
    DATA
INNER JOIN
    DATA AS
    PAST ON
    PAST.MONTHLY < DATA.MONTHLY
GROUP BY
    DATA.MONTHLY
ORDER BY
    DATA.MONTHLY ASC